1. Field
The disclosed embodiments belong to the field of aircraft powered by jet engines such as transport civil aircraft.
More particularly the disclosed embodiments relate to an aircraft including at least an engine installed within the fuselage tail section in order to be used only in certain running phases of the aircraft on the ground or in flight.
2. Brief Description of Related Developments
For safety reasons and in order to fulfill the certification lawful requirements, the transport aircraft comprise two or several engines to survive to engine failure cases during the various flying, takeoff, cruising or approach and landing phases.
While respecting the certification criteria and the operational constraints, the choice of the number and the characteristics of the engines is the result of compromises implying the desired, or required, performances of the aircraft in its various flying phases and in the various probable operating situations of the engines.
However, for industrial and operational reasons, the various engines of an aircraft in commercial exploitation are of the same model which has advantages in the field of the engines maintenance but does not present necessarily an optimum in term of thrust balance, carried mass for the propulsion and aerodynamic drag.
Moreover, to ensure an autonomous production of energy, electricity, compressed air . . . , aboard an aircraft in order to feed the various aircraft systems when the engines are stopped, on the ground before the startup of the engines, or in an exceptional way, in flight in the event of generations loss on the engines, the civil aircraft very frequently comprise an auxiliary power generator, generally designated by APU for Auxiliary Power Unit, dedicated to this service.
A drawback of the APU systems comes from the mass that they represent and which must be permanently transported mainly for a ground use.
A considered solution, presented in the U.S. Pat. No. 6,247,668, consists in using a particular jet engine to provide the functions of the APU when it is necessary to have an autonomous energy generation and to provide a complementary propulsion thrust when such a complementary thrust can prove to be useful or necessary.
The particular jet engine is not used when no additional energy or thrust source is necessary what makes it possible to maintain the particular jet engine at stop in order to optimize the fuel consumption.
The particular jet engine, designated by APTU, is fitted within the fuselage tail section, in the practice, approximately at the location of the majority of the APU on the existing aircraft, so that it generates a thrust directed backwards of the aircraft.
An air intake to feed the APTU with a scoop shape on the top of the fuselage has a closed position when the APTU jet engine is not running and this APTU jet engine has not necessarily a thrust identical to that of the other ordinary propulsive engines.
However, this solution was never been implemented on an aircraft and, except using relatively small engines closer to a conventional APU than to an engine, many problems of mechanical installation and aerodynamic integration which are not solved today arise.